Psychology
A doll named Sally reveals when kids learn other people can be wrong
In the Sally-Anne test, a doll leaves her ball in a basket, then another doll secretly moves it while she's away. Children under four insist Sally will look in the new spot — they can't yet grasp she still believes it's in the basket. Passing this false-belief test marks the emergence of 'theory of mind': modelling a mind as different from your own.